Draftsman&#39;s protractor.



n. N. VAN BU'SKIRK. DRAFTSMANS PROTRYACTOR.

APPLICATION FILED NOV. 25, 192.

Patented Oct. 26, 1915.

3 SHEETS-SHEET I.

ATTORNEY COLUMBIA PLANOGRAPH CO-. WASHINGTON, D C.

R. N. VAN BUSKFRK. DRAFTSMAN'S PROTRACTOR. APPLICATION FILED NOV. 25, 1912.

Patented Oct, 26, 1915.

S SHEETS-SHEET 2.

wfinssszs RTTORHEY COLUMBIA PLANCIGRAPH c0., WASHINGTON, D. c.

Patented Oct. 26, 1915.

3 SHEETS-SHEET 3.

\NITHE55ES ATTORNEY COLUMBIA PLANouRAPH CO, WASHINGTON. D. c.

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ROBERT 1\T. VAN BUSKIRK, 0F DETROIT, MICHIGAN.

DRAFTSMANS PROTRAGTOR.

Specification of Letters Patent.

Patented @ct. 26, 1915.

Application filed November 25, 1912. Serial No. 733,250.

To all whom it may concern:

Be it known that I, ROBERT N. VAN Bus- KIRK, a citizen of the United States, residing at Detroit, county of Wayne, State of Michigan, have inventeda certain new and useful Improvement in Draftsmens Protractors, and declare the followin to be a full, clear, and exact description 01: the same, such as will enable others skilled in the art to which it pertains to make and use the same, reference being had to the accompanying drawings, which form a part of this specification.

My invention relates to the construction of draftsmens protractors, and my main ob ject is to produce a high grade instrument that can be marketed at a low price. I attain this object in the device illustrated in the accompanying drawings in which Figure l, is a perspective view of a protractor embodying my invention. Fig. 2, is a perspective view of a portion of the base showing in detail the hole and recess or notch for the clamping screw and clamp heel respectively. Fig. 3, is a detail perspective view of the clamp and screw; Fig. 4, is an underside view of the assembled protractor. Fig. 5, tea cross section taken on the line 11 of Figs. 1 and 4:. Fig. 6, is a cross section taken on the line 22 of Figs. 1 and 4c. Fig. 7, is a cross section taken on the line 3-3 of Figs. 1 and 4.. Figs. 8 and 9 show an optional construction of the instrument as a whole with reversed relative positions of the base and sector.

A is a sheet metal die blanked and pressed base having two depressed straight edges or, and a, at right angles to each other, the bisected angle of which passes through the point P, at which the base A, is pivoted to the sector B, the depressed portions a, and a, rest upon the paper partly supporting the protractor; the object of the metal being bent down as shown in Figs. 5, and 6, to stiffen the base A, allowing theuse of very thin metal which aids in making a light instrument. i

c, and c, are lips, which are formed on the base A, and lie in the same plane with the straight-edges a, and a, and extend underneath the sector B, to hold the circular edge of the sector up in the proper plane,

especially when the clamping nut E, is loosened for the purpose of changing angles; these lips also add rigidity to the assembled instrument, even when the base A, and sector B, are securely clamped together, inasmuch as both the base and sector are held in the proper plane in relation to each other at the three points P, c, and c, which are triangularly located. See Fig. 4.

(Z, is a segmental portionof the base A, depressed from said base to the same plane with, and abutting the sector B, upon which is stamped two sets of Vernier graduations reading to five minutes each in opposite directions from the bisected angle of the edges 0/, and a, said graduations are numbered for each fifteen minutes from said bisected angle.

e, is an aperture in the base A, through which the clamping screw '1), extends vertically.

' f, is a notch in the base A, in which the clamp heel 2', is seated and held from turning in a horizontal plane.

g, are openings in the base A, for the purpose of reducing weight.

B, is a sheet metal die blanked and pressed sector of an approximately semi-circular form, upon which are stamped graduations in degreesto the extentof 110 degrees, which graduations are located along the periphery of the upper side and substantially in the middle of the sector arc, and are numbered for each 10 degrees from 0 to 90 degrees in both directions beginning at the tenth graduation from either end; the extra unnumbered ten graduations at each end are neces sary for the Vernier readingsbetween 80 and 90 degrees; the sector B, being pivoted to the base A, at the point P, the center of the outer circular edge of the sector.

I), is a depressed portion of the sector B, which forms a straight-edge, the length of which is approximately equal to the diameter of the circle of which the sector is a part, and rests upon the paper partly supporting the protractor; the fact of the metal being bent down as shown in Figs. 5 and 7,

insures extra stiffness to the sector B, allowing the use of very thin metal which aids in making a light instrument.

C, is a sheet metal die blanked and pressed 7 clamp which lies substantially underneath notch f, of the base A. r

the sector B, and into which the clamping screw D, is permanently fixed. The clamp is drawn up against thesector B, which 1s held securely in place against the base A, by the thumb nut E, operating upon the threads of the clamping screw D.

i, is the heel of the clamp C, whlch is turned upright and fits snugly into the j j, are shoulders on the heel i, of the clamp C, which bear up against the sides of the notch f, of the base A, when the clamp "i drawn tightly against the sector B.

70 7c, are shoulders on the heel i, of the clamp O, which fit snugly against the edges of the notch f, of the base A, preventing the clamp C, from turning when adjustingthe thumb nut E. i

Z, is the end of the clamp C, which bears up against the inner circular edge m, of the sector B, holding thesector tightly against the base a n n, are openings in the sector B, for the purpose of reducing weight.

F,.is a pivot bearing having an enlarged end forming a shoulder which bears up against the underside of the sector B, said on the pivot bearing F.

H, is a washer interposed between the thumbnut E, and thebase A, and fitting loosely over thev clamping screw. D; this washer may be of spring steel and the two halves bent at a slight angle with each other when free, for the purpose of holding the clamp C, up in place when the thumb nut E, is loosened. J, is an indicatorstamped upon the base A,'to indicate the angle between the straightedges a and b. 1

K,.is an indicator stamped upon the base A, to indicate the angle between the straightw edges a and b.

, While I have described the sector as placed under the base as shown, it is obvious that the relative positions of the base and 6O sector may be reversed in this respect.

- With the above construction a lighter instrument can be made because of the minimum number of parts as well as the very thinstock whichcan be used owing to the acquired stiffness by bending. And because of said reduction of parts, and of the die stamped graduations, and the other described simplifications, the cost to mannfacture will be unusually low for so high a grade an instrument.

What I claim is,-

1. In a protractor, the combination of a base, a sector lying under the base, said base having clips 0 c bent downwardly and under said sector, said base having a portion bent downwardly so that its edge shall abut against the curved edge of said sector, said abutting edges being provided with cooperating scales.

2. In a protractor, the combination of a base having straight edges a a bent downwardly, a sector lying below said base and being provided with lips c 0 extending under said sector, and having their lower surfaces in the plane of the supporting portion of said base.

3. In a protractor, the combination of a base, a sector lying under said base, said base being provided with a notch f, a clamp upon said base adapted to engage under said sector and provided with a heel 2', adapted to engage in said notch.

4. In a protractor, the combination of a base and a sector, a pivot bearing hax'ing a flattened edge portion joining said base and sector, said sector being provided with a shoulder h, against which said flat portion bears.

5. In a protractor, the combination of a base and a sector arranged under said base of a clamp having an upwardly extending heel with shoulders adjacent to the lower end thereof, said base being provided with an aperture 7, said heel being adapted to engage in said aperture and said shoulder against the surface of said base.

6. In a protractor, the combination of a base, a sector pivoted to the base and having one face near its circumferential edge slidingly engaging one face of the base and members attached to the base at widely spaced points thereon for engaging the other face of the sector adjacent its circumferential edge to guide the said sector in its rotative movement with respect to the base.

7. In a protractor, the combination of a base having two intersecting straight edges that can rest on the surface where the protractor is used, a sector pivoted to the base, the main portion of the base being raised above the surface to provide a span greater than the thickness of the sector, the said sector provided with a straight edge capable of resting upon the said surface when used, the main part of the sector being raised above the said surface but somewhat less than the spacing of the main part of the base, the said sector being thereby adapted In testimony whereof, I sign this specification in the presence of two Witnesses.

ROBERT N. VAN BUSKIRK.

' Witnesses:

VIRGINIA O. SPRATT, Aeuns M. HIPKINS.

to swing in under the base but spaced from the underlying surface, means for pivoting the sector to the base, and means for holding the circumferential edge of the sector against the under side of the base and securing the same in various angular relations with respect to the base.

topics of this patent may be obtained for five cents each, by addressing the Commissioner of Patents. Washington, D. G. 

